As the clearing crew proceeds, many fences are crossed. The clearing 

 crew will erect temporary fencing and reroute fences where needed. They may 

 also clear and grade temporary roads to the pipeline route for easier access 

 by supply vehicles and personnel. 



In most upland areas, a large rotary ditcher is used to dig the trench. 

 The ditcher moves along on tracks and digs a continuous hole, the depth of 

 which depends on the size pipe to be laid. The depth is selected so that the 

 top of the pipe will be about one meter below the surface of the land. 

 Federal regulations (49 CFR 192,327; 49 CFR 192.248) prescribe minimum depths 

 for all natural gas pipelines and liquid petroleum pipelines used in interstate 

 commerce. In rural areas, a minimum of 0.75 m (30 inches) is required between 

 the pipeline top and ground level. In urban areas, the minimum is 0.92 m 

 (3 ft), and in deepwater port safety zones and inland water bodies greater 

 than 30 m (100 ft) wide, the minimum depth for liquid pipelines is 1.2 m 

 (4 ft). Pipeline contractors generally follow these guidelines even for 

 intrastate liquids pipelines since they may be used in future interstate 

 commerce. The spoil from the hole is stacked in a continuous row on one side 

 of the ditch. The other side remains clear so equipment can move right up to 

 the hole. 



Rocks, stumps, and other pipelines are encountered in the ditching process. 

 Obstructions may be blasted if they are large, and the rubble is removed by 

 dragline or backhoe. Usually, where pipelines cross, the new pipeline will be 

 placed under the existing one. Roads, highways, and railroads are crossed at 

 many points. The road may actually be cut by the ditcher and a temporary road 

 crossing made from heavy beams and steel plates. For major highways and 

 railroads, a road-boring machine may be used to drill a hole under the road. 

 The hole is then lined with conduit through which the pipeline will pass. 



Rainwater and high levels of groundwater often result in water collecting 

 in the hole. Pumps are used to remove the water and place it on the upland 

 area adjacent to the work site. 



Trucks enter the right-of-way carrying pipe. There may be access roads 

 every few miles, so supply trucks do not have to drive the entire distance on 

 the right-of-way road. The pipe is set off to the side by side-boom tractors. 

 When bends are needed in pipe, special track-mounted machines are used. 



The joints for pipelines that carry high pressures are welded. The end 

 of the pipe is cleaned and squared by grinding and cutting if necessary. The 

 pipe is lifted by side boom, aligned, clamped, and welded by hand or by auto- 

 matic welding equipment. The initial bead holds the pipe aligned and allows 

 the clamps to be removed and the next section to be prepared. Then other 

 teams of welders with varying types of equipment may add one to four more 

 beads, depending on pipe thickness. 



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